READIT-2007 - Indira Gandhi Centre for Atomic Research

epresentation, provenance, fixity and context information. Encapsulation is
considered a key element of emulation.
Universal Virtual Computer (UVC): The concept of Universal Virtual computer
was developed by Raymond Lorie. It uses elements of both migration and emulation
which allows digital objects to be reconstituted in their original form. The UVC
concept consists of the UVC itself, a logical data scheme with type description, the
UVC program (format decoder) and the logical data viewer.
Authenticity: The quality of being reliable or trust worthy.
Fixity: The state or quality of being fixed or unchanged.
Compression: Compression can be applied to many different kinds of digital
objects, and can be either lossless. Lossless compression is fully reversible, so when a
file is decompressed, it is bit for bit identical to its original. Lossless compression is
always used for encoded text and may be used for images sound, video, etc.,
depending on considerations such as bandwidth, quality, and storage requirements.
4. ISSUES IN DIGITAL PRESERVATION
• Obsolescence
File formats and software:
Determine the file format status of your digital holdings. What formats and
versions are represented, in what quantities? Such an inventory is an important step
towards managing file format risk. The range of formats in use should be consolidated
to minimize duplication and eliminate problem formats. This process is known as
normalization.
Hardware:
New computing hardware opens the door to new and improved software,
leading to software and file format obsolescence. The new software will not run on
old hardware, further exacerbating hardware obsolescence. At the same time, the new
hardware introduces other new technologies such as peripheral connections and
storage devices (e.g., USB keys, pen drives and CD drives replace floppy disks).
These changes force older peripherals into retirements along with their compatible
computers.
Media format:
There are three commonly used categories of digital storage media: disk, tape
and solid state. The nature of the physical media on which digital data is stored
presents a major challenge to the preservation of digital content. The great variety of
media types, their often rapid obsolescence from technology from technology change,
and their vulnerability to Physical degradation all contribute to problems.
Physical Degradation:
Besides the issues around obsolescence of file formats, applications, operating
systems and hardware, there is the more basic question of how to deal with the fact
that media physically degrade or become obsolete. How long will various media types
last? Thesis considerable controversy around the issues with Kodak claming in one
report that its writable CD’s would last 217 years under certain conditions while
others observe that such media start to degrade after only a couple of years.
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